1. Field of the Invention
This invention relates to the extraction of (semi) shells from forming machines employed in the shell moulding process. More particularly the invention concerns a method and the relative equipment for the rapid and safe extraction of the hot (semi-) shells and for their overturning through 180 degrees relative to the position of lift-off from the forming machine.
2. The Prior Art
It is well-known that for the preparation of shell castings it is necessary to prepare the shells from a sand-resin paste which is spread on the mould end heated by means of methane jets; generally the forming machine produces two semi-shells or indeed two pairs of semi-shells at a time.
Extraction of the semi-shells has always involved many problems; it is indeed true that the forming machines are furnished with bars which, as soon as the moulding has been carried out, lift the semi-shells from their place facilitating their extraction, but it is also true that the workman who grips the hot semi-shells with gloves is struck by the intense heat from the jets and the shells themselves and has to work in conditions that are uncomfortable, besides being dangerous. To avoid these drawbacks use has been made of extracting machines consisting essentially of extracting forks with a forward and backward movement which slip beneath the semi-shells the moment that the extracting bars raise them from their forming position. When these bars descend the semi-shells perch on the forks which execute a backward movement withdrawing the semi-shells from their place by about 1 m. On completion of this movement the forks can generally also turn through a vertical axis of 45 or 90 degrees carrying the semi-shells into a position which is off-set from the above-mentioned rotation angle, relative to the axis passing through the middle-line of the forming machine and the extracting machine. Here the workman takes hold of the semi-shells in order to separate them from one another, overturn them, possibly insert the core and put them into the machine which glues them in pairs. Conventional shell-extracting machines present various disadvantages: they displace the shells little, which means that even in the withdrawn position (generally a matter of 1 meter) and possibly rotated (45 or 90 degrees) the workman is still always exposed to a strong heat (or to the danger of bursts of flame) from the forming machine; the semi-shells are still too hot and call for considerable effort in their lifting but above all in their inverting through 180 degrees, i.e. turning them upside down.
In effect while it is true that the forks have moved them from the forming machine, they have left them in the original position (base upwards) which they had in the moulding machine. Lastly the conventional machines are bulky in themselves and moreover call for much space because the workman besides moving the semi-shells must also turn them before placing them on the bench for the core-assembly and glueing operations.